The present invention relates to an airbag system for protecting an occupant in a vehicle such as a car in an event of a car crash. More particularly, the present invention relates to an airbag system including an airbag in which an interior thereof is partitioned into a plurality of chambers.
In an airbag system, a gas generator inflates an airbag toward an occupant, and the inflated airbag receives a body of the occupant. Japanese Patent Publication (KOKAI) No. 2000-177527 has disclosed a side airbag system in which a lower part of the airbag is inflated at an inner pressure higher than that of an upper part for receiving a lumbar part of the occupant. FIG. 7 is a side view of a seat equipped with the side airbag system disclosed in the reference, and FIG. 8 is an enlarged sectional view showing a section 8 in FIG. 7.
An airbag 18 is partitioned into an upper chamber 20 and a lower chamber 22 with a seam 24. A rear end of the seam 24 is located slightly away from a rear rim of the airbag 18, and a cylindrical housing 30 is placed in a space between the rear end of the seam 24 and the rear rim of the airbag 18. A rod-shaped gas generator 36 is placed in the cylindrical housing 30. Upper and lower ends of the cylindrical housing 30 are formed with pipe clips 32 and 34 for fixing the gas generator 36. The pipe clips 32 and 34 seal portions between the gas generator 36 and the cylindrical housing 30. The pipe clips 32 and 34 are attached to mounting sections 26 of a seat back 14.
The cylindrical housing 30 has upper-chamber discharge ports 42 for discharging gas from the gas generator 36 into the upper chamber 20, and lower-chamber discharge ports 44 for discharging gas into the lower chamber 22. Each of the lower-chamber discharge ports 44 has an opening larger than those of the upper-chamber discharge ports 42. Therefore, when the gas generator 36 is activated to inflate the airbag 18, an inner pressure of the upper chamber 20 becomes about 0.5 bar and an inner pressure of the lower chamber 22 becomes about 1.5 bar.
In Japanese Patent Publication No. 2000-177527, the side airbag system has the cylindrical housing 30. When the lower chamber 22 of the airbag 18 receives the occupant, the gas in the lower chamber 22 flows into the upper chamber 20 through the cylindrical housing 30. Therefore, it is difficult to maintain the gas pressure in the lower chamber 22 at a high level for long time.
In view of the problem described above, an object of the present invention is to provide an airbag system in which it is easy to maintain a gas pressure at a part of an airbag, for example, a lower part of the airbag, at a high level for sufficiently long time.
Further objects and advantages of the invention will be apparent from the following description of the invention.
According to the present invention, an airbag system includes an airbag having a surface facing an occupant and an opposite surface facing a car body in an inflated state, and a gas generator for generating gas to inflate the airbag. The airbag further includes an inner bag to be inflated first and a check valve for preventing the gas from flowing from the inner bag to the airbag. In the airbag system, after the inner bag is inflated, the gas is supplied only to the airbag to inflate the same.
According to the present invention, when the gas generator is activated, the inner bag is inflated first. The inner bag may be disposed at a lower part of the airbag, so that the lower part of the airbag is inflated at an early stage. In the airbag system, the check valve is provided for preventing the gas from flowing from the inner airbag to the airbag. Therefore, it is possible to maintain an inner pressure of the inner bag at a high level for a long time. The airbag system can protect an occupant not only in a case of a car crash but also roll over.
According to the present invention, the airbag system may further include connection means for connecting the inner bag and the gas generator. The connection means disconnects the inner bag from the gas generator when the gas pressure in the inner bag exceeds a predetermined value, so that the gas generator supplies the gas only to the airbag.
According to the present invention, the inner bag may be connected to the gas generator through the connection means. When the gas pressure in the inner bag exceeds a predetermined value, the connection means is released.
According to the present invention, the connection means may be an extension extending from a gas inlet port of the inner bag and having a tear seam. The tear seam is torn off to separate the extension from the inner bag when the gas pressure in the inner bag exceeds a predetermined value. With such a structure, when the gas pressure in the inner bag exceeds the predetermined value, the inner bag is securely separated from the gas generator and the gas generator quickly inflates the airbag.